In learning xhtml and css I have come accross these organisations referenced a few times, are they worth taking notice of or not really?

So far I have worked under the impression that they are worth taking notice of and have coded accordingly.

So are they? As I am still learning I might aswell learn how to do it right and I just want to know if including code to help screen readers etc work better is worth it or not?

Is it better to learn how to hand code or use an application or some sort of mix between the 2. I am currently using dreamweaver but had coding in it as the colours make the code easier to read.